Q&A - P4 Math

[smartmummy]

Another method drawing model.u can found some qns here solved by using model

[php]

AgonyMum:

Hi MathIzzzFun, help needed: Thanks in advance!

Excess-Shortage Problems
2. May walks to school.If she walks at a speed of 60m per minute, she will be late for 5 mins. If she walks at a speed of 75m per min, she will be early for school by 2 mins. What is the distance between her house and her school?

Thanks very much!

Using Maths Olympiad Method

60m/min for 5 mins --> 60 x 5 = 300m
75m/min for 2 mins --> 75 x 2 = 150m

Time Taken --> (300 + 150) div (75 - 60) = 30 mins

Distance --> (30 x 60) + 300 = 2100m

For checking, (30 x 75) - 150 = 2100m

[smartmummy]

Hi php!

This method i found in a pastpaper.here also use.

php:

AgonyMum:

Hi MathIzzzFun, help needed: Thanks in advance!
Excess-Shortage Problems
1. There are some men carrying bicks. If each man carries 4 bricks, there wil be 7 bricks left. If each man carries 5, there will be a shortage of 2 bricks. How many bricks are there?

Can I use : Multiples of 4 (add7) 11,15,19,23,27,31,35,39,43
Multiples of 5(minus2) 3,8,13,18,23,28,33,38,43
When I use this method, I realised that there are 2 answers - 23 and 43.Only 43 seems to be the correct answer. Am I doing something wrong? Is my method correct or is there another more effective method?

Thanks very much!

Using Maths Olympiad Method

4 bricks --> +7
5 bricks --> -2

No of men --> (7 + 2) div (5 - 4) = 9

No of bricks --> (9 x 4) + 7 = 43

For checking, (9 x 5) - 2 = 43

[Nebbermind]

smartmummy:

Hi php!

This method i found in a pastpaper.here also use.

php:

[quote=\"AgonyMum\"]Hi MathIzzzFun, help needed: Thanks in advance!
Excess-Shortage Problems
1. There are some men carrying bicks. If each man carries 4 bricks, there wil be 7 bricks left. If each man carries 5, there will be a shortage of 2 bricks. How many bricks are there?

Can I use : Multiples of 4 (add7) 11,15,19,23,27,31,35,39,43
Multiples of 5(minus2) 3,8,13,18,23,28,33,38,43
When I use this method, I realised that there are 2 answers - 23 and 43.Only 43 seems to be the correct answer. Am I doing something wrong? Is my method correct or is there another more effective method?

Thanks very much!

Using Maths Olympiad Method

4 bricks --> +7
5 bricks --> -2

No of men --> (7 + 2) div (5 - 4) = 9

No of bricks --> (9 x 4) + 7 = 43

For checking, (9 x 5) - 2 = 43

[/quote]The problem is that we tend to try to remember some formula for this kind of math indeed of visualizing in our mind.

Given that there are 7 left if each man gets 4, and if u give 5, u r 2 short, therefore u know u needed 9. Therefore the are 9 men.

Sometimes it can be tricky but we shd try to rely less on remembering formula

[php]

Nebbermind:

smartmummy:

Hi php!

This method i found in a pastpaper.here also use.[quote=\"php\"]Using Maths Olympiad Method

4 bricks --> +7
5 bricks --> -2

No of men --> (7 + 2) div (5 - 4) = 9

No of bricks --> (9 x 4) + 7 = 43

For checking, (9 x 5) - 2 = 43

The problem is that we tend to try to remember some formula for this kind of math indeed of visualizing in our mind.

Given that there are 7 left if each man gets 4, and if u give 5, u r 2 short, therefore u know u needed 9. Therefore the are 9 men.

Sometimes it can be tricky but we shd try to rely less on remembering formula[/quote]Actually this kind of question is about multiplication and division...
using model will be able to visualise better...

once the kid can visualise the model, then the MO formula method will make more sense....imho...

[MathIzzzFun]

AgonyMum:

Hi MathIzzzFun, help needed: Thanks in advance!

Excess-Shortage Problems
1. There are some men carrying bicks. If each man carries 4 bricks, there wil be 7 bricks left. If each man carries 5, there will be a shortage of 2 bricks. How many bricks are there?

Can I use : Multiples of 4 (add7) 11,15,19,23,27,31,35,39,43
Multiples of 5(minus2) 3,8,13,18,23,28,33,38,43
When I use this method, I realised that there are 2 answers - 23 and 43.Only 43 seems to be the correct answer. Am I doing something wrong? Is my method correct or is there another more effective method?

2. May walks to school.If she walks at a speed of 60m per minute, she will be late for 5 mins. If she walks at a speed of 75m per min, she will be early for school by 2 mins. What is the distance between her house and her school?

Thanks very much!

Hi

php has provided the solutions.

Are these questions from the school ? First time seeing a speed question (Q2) manifesting as gap/diff question - this would be easily solved using time ratio, for P6. I have added the models to make it easier to visualize the solution:

http://i45.tinypic.com/fef2n8.png\">

Here are some similar questions that were discussed before
- http://www.flickr.com/photos/62167097@N02/6960200923/in/photostream
- http://www.flickr.com/photos/62167097@N02/6967105663/in/photostream

cheers.

[AgonyMum]

Hi php, thanks very much for your soution :)I think I sort of get it. Shall have to look through again to familiarise myself in order to explain to my kid.


Hi MathIzzzFun, thanks for the visual help with your diagram
These questions are not from school.My child got them from a classmate who attended some Math tuition class.

All Math Experts, teachers and parents, do keep up your good work in helping clueless parents like myself.Very grateful to you all. Kudos!

[Nebbermind]

Alternatively


If May continue to walk at 75m/min for 7 mins (the same amt of time she needs if she is walking at 60m/min), she would have walked an extra (7 x 75m) = 525m.

Since she gains 15m every min if she walk at 75m/min, therefore she took (525/15 = 35) 35 mins to walk the extra distance, which is also the time she'll take @ 60m/min for the journey.

This will translate to (35 x 60) 2100m for dist between her home and school.

My boy taught me this method which I immed understood....donch need to memorize any formula.

[chloecube]

Fara made 520 more cakes than Sue. After Fara sold 20 cakes and Sue sold 40 cakes, Fara had 5 times as many cakes as Sue. How many cakes did Fara have at first?


ans is 695, can someone show me the working? thks

[tianzhu]

chloecube:

Fara made 520 more cakes than Sue. After Fara sold 20 cakes and Sue sold 40 cakes, Fara had 5 times as many cakes as Sue. How many cakes did Fara have at first?


ans is 695, can someone show me the working? thks

Hi

A neat way is to use MD.

Fara ------ 5 units + 20
Sue ------ 1 unit + 40

5 units + 20 ------ 1 unit + 40 + 520
1 unit ------- 135

Fara ------ (5*135) + 20 ------- 695

Best wishes